Ein. Isolation of Primary Chondrozyten Ernte 10-15 volle Dicke Knorpel Scheiben von den Gelenkflächen des tierischen Gelenken (zB das Mittelhandknochen-Phalangealgelenk von ausgewachsenem Skelett Kühen von einem lokalen Schlachthof gewonnen). <ol><li> Ort Knorpel Scheiben in einer 100 mm Petrischale und Inkubieren in 20 ml 0,5% Protease in Ham-F-12 (w / v) für 2 Stunden bei 37 ° C. Spülen Sie drei Mal in Ham-F-12 Kulturmedien und inkubieren mit 20 ml 0,15% Collagenase A in Hams F-12 Kulturmedien über Nacht bei 37 ° C. </li><li> Filtern der Zellsuspension durch ein 200 mesh-Sieb-Filter in einen sauberen Teller. Waschen Sie den Filter mit 5 ml Ham F-12 und zu dem Gericht. Übertragen der Zellsuspension in ein 50 ml konischen Röhrchen. Waschen Sie die Petrischale mit 10 ml Ham F-12 und zu dem konischen Rohr. </li><li> Zentrifugieren bei 600-800 rcf für 6-8 min bei Raumtemperatur. </li><li> Überstand, wodurch nicht th störene Zellpellet und in 40 ml Ham-F-12 Kulturmedium erneut zu suspendieren. </li><li> Zentrifugieren bei 600-800 rcf für 6-8 min. </li><li> Wiederholen Schritte 1.4 und 1.5 noch zweimal mit insgesamt 3 mal. Vor dem Zentrifugieren zum dritten Mal, das Pellet über Agitation und erhalten eine 500 ul Aliquot zur Zellzählung. </li><li> Zählen lebensfähigen Zellen unter Verwendung des Trypan-Blau-Ausschluss-Methode 9 mit einem Hämozytometer und eines invertierten Lichtmikroskops. </li><li> Überstand und resuspendieren des Pellets in einem Volumen von Ham-F-12 Medium, um den gewünschten Einsaatdichte verdoppeln (z. B. 20 x 10 6 Zellen / ml für eine Endkonzentration von 10 x 10 6 Zellen / ml nach der Verkapselung). </li></ol> 2. Chondrozyten-Agarose Hydrogel Encapsulation <ol><li> Wärme 0,8 g autoklavierten Typ VII Agarose in 20 ml sterilem 1x PBS (pH 7,4) auf einer Heizplatte bei 120 ° C bis zur Auflösung. Einmal gelöst, die Hitze auf 60 ° C höhere Temperaturen als will beeinträchtigen die Lebensfähigkeit der Zellen. </li><li> In einem 50 ml konischen Röhrchen wird gründlich gemischt gleichen Volumina der Zellsuspension mit der doppelten gewünschten Konzentration aus Agarose (z. B. 4% Agarose Suspension für eine abschließende 2% Agarose Hydrogel). Vermeiden Sie die Erstellung von großen Blasen, wie sie die Lebensfähigkeit der Zellen beeinflussen können und bauen Lebensdauer. </li><li> Sorgfältig Aliquot von 10 ml der Chondrozyten-Agarose Mischung in eine 60 mm Petrischale Durchmesser, unter Vermeidung der Bildung großer Blasen. </li><li> Lassen Sie stehen für 30 min bei Raumtemperatur bis geliert. </li><li> Zu erhalten, wie viele Chondrozyten-Agarose Hydrogel Proben nach Bedarf (typischerweise 20-30) mit einem 4 mm Biopsiestanze. </li><li> Messung und Aufzeichnung der physikalischen Abmessungen (Durchmesser und Höhe) von repräsentativen Proben mit einem Mikrometer. Konstrukte sollte etwa 5 mm betragen in der Höhe, verwerfen Proben aus einem Bereich, wo der Probenhöhe Varianz größer als 2% erhalten. </li><li> Übertragen Proben zu einem neuen 60 mm Petrischale und Ergänzungmit 10 ml komplettem Medium (z. B. 20% fötalem Rinderserum in Ham-F-12 Kulturmedium mit 20 mM HEPES, 100 ug / ml Ascorbinsäure und 2x Antibiotika / Antimykotika). </li></ol> 3. Mechanische Stimulation und Radiomarkierung von Chondrozyten-Agarose Hydrogele <ol><li> Autoklaven werden die metallischen Komponenten des Kompressions-rig. Sterilisieren Sie die Kunststoffteile mit 70% Ethanol (über Nacht) und UV-Licht (mindestens 15 min). </li><li> Konstrukte Umfallen, mit Pinzette Platz 12 sterile Plastik Halteringe (mit einem Innendurchmesser größer als der Durchmesser Konstrukt) (n = 6, Proben und Kontrollen) innerhalb der Vertiefungen einer 24-Well-Kulturplatte zu halten. </li><li> Mit einer Pinzette, transferieren es vorsichtig die Chondrozyten-Agarose Hydrogele aus der Petrischale auf den 24-Well-Platte, die Sicherung jedes in einem Haltering. </li><li> Übertragen 400 ul komplette Medien (zB 20% FBS in Ham-F-12 Kulturmedium mit 20 mM HEPES, 100 ug / ml Ascorbinsäure und2x Antibiotika / Antimykotika) zu jedem Probenbehälter. </li><li> Montieren Sie die sterilisiert Kompression rig (Abbildung 1) und befestigen Sie die Platten mit Stellschrauben. Bringen Sie die Kompression rig auf die 24-well Platte. </li><li> Lösen und wieder sichern die Stellschrauben Platte-Hydrogel-Kontaktlinsen (spannungslosen Zustand) zu etablieren. </li><li> Legen Sie die zusammengebauten Kompression rig in eine Mach-1 Mikromechanische Testing System. Sichere rig auf die vertikale Stufe über Fixierstift und einrasten mit Stellschraube. Entfernen Sie den Abstand jig. </li><li> Anwenden dynamischen Druckbelastung an gewünschten Amplitude (z. B. 10% Dehnung Amplitude auf der ursprünglichen Höhe der Proben basierend), Frequenz (zB 1 Hz) und Dauer oder Anzahl der Zyklen (zB Zeitintervallen bis zu 60 min). </li><li> Nach Abschluss der mechanischen Stimulation, ersetzen Sie den Abstand jig, lösen Sie die Fixierstift Stellschraube und entfernen Sie die Kompression rig und Kultur Platte aus dem Mach-1 Mikromechanische Testing System. </li&gt; <li> Radiomarkierung Zell-Hydrogel-Konstrukte durch Ergänzung der Medien mit 5 uCi gewünschte Isotop (zB [3 H]-Prolin-Protein-Label für Chondrozyten-spezifische Kollagen-Synthese und [35 S]-Schwefel für Proteoglykan-Synthese). </li><li> Inkubieren der radiomarkierten Konstrukten für 24 h bei 37 ° C, 5% CO 2 10. </li><li> Ernten Sie die radioaktiv markierten Hydrogel Konstrukten und spülen 3 mal in 1x PBS (pH 7,4) auf eine nicht rechtsfähige Isotop entfernen. Ausgewählte Proben unter Verwendung von Papain (40 ug / ml in 20 mM Ammoniumacetat, 1 mM ethyldiaminetetraacetic Säure und 2 mM Dithiothreitol bei 65 ° C für 72 h). </li><li> Assay Digest für DNA-Gehalt mit dem PicoGreen Farbstoff Assay 11 und eingebauten Isotops Aktivität, normiert auf DNA-Gehalt von β-Flüssig-Szintillationszählung 12,13 unmittelbar folgenden Papainverdau. </li></ol> Hinweis: Der Kauf und die Entsorgung von radioaktiven Materialien (Abfälle Isotope und Artikeldie möglicherweise in Kontakt radioaktiver Stoffe gekommen sind) müssen den einschlägigen institutionellen (und / oder staatlichen) Vorschriften und Verfahren für die sichere Handhabung und Entsorgung von radioaktiven Substanzen. 4. Repräsentative Ergebnisse Bovine Gelenkchondrozytenprobe-Agarose Hydrogele Konstrukte (2% Agarose mit 10 x 10 6 Zellen / ml eingekapselten Zellen) wurden mechanisch mit einer Amplitude von 10% Stauchung bei einer Frequenz von 1 Hz für 20 bis 60 min (oder 1.200 bis 3.600 Zyklen angeregt ) und im Hinblick auf DNA-Gehalt und extrazellulären Matrix-Synthese durch Einbau Radioisotop. Und extrazellulären Matrix-DNA-Synthese wurde in einer Dosis-abhängigen Weise beeinflusst. DNA-Gehalt zeigte eine signifikante Abnahme von 35% als Ergebnis von 20 oder 30 min der Stimulation (p &lt;0,01), während 60 min Stimulation zeigte keinen Effekt (Abb. 2). Knorpel-spezifische Kollagen und Proteoglykan-Synthese (bestimmt durch [3 H]-Prolin und[35 S]-Schwefel Einarbeitung jeweils) zeigten signifikante Anstiege von etwa 60% in Reaktion auf 20 bis 30 min der Stimulation (p &lt;0,01), 60 min mit der Stimulation aufweist keinen beobachtbaren Effekt (Abb. 3). <img src="/files/ftp_upload/4229/4229fig1.jpg" alt="Abbildung 1" /> . Abbildung 1 Schematische Darstellung des custom-built dynamische Kompression rig zur Stimulierung Chondrozyten-Agarose Konstrukte. Links: Assembled rig. Rechts: Explosionszeichnung zeigt Einzelkomponenten. <img src="/files/ftp_upload/4229/4229fig2.jpg" alt="Abbildung 2" /> Abbildung 2. Veränderungen in der DNA-Gehalt der Chondrozyten-Agarose Hydrogele mechanisch unter einer 10% Stauchung Amplitude bei 1 Hz für 20 bis 60 min (Mittelwert ± SEM, n = 6/Gruppe) stimuliert. Abbildung 3. Veränderungen der extrazellulären Matrixsynthese (Kollagen und Proteoglykane) der Chondrozyten-Agarose Hydrogele mechanisch unter 10% Stauchung Amplitude bei 1 Hz für 20 bis 60 min (Mittelwert ± SEM, n = 6/Gruppe) stimuliert.

<ol>
	<li>Grodzinsky, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cartilage+tissue+remodeling+in+response+to+mechanical+forces.">Cartilage tissue remodeling in response to mechanical forces.</a> Annual Review of Biomedical Engineering. 2, 691-713 (2000).</li><li>Kuettner, K. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemistry+of+articular+cartilage+in+health+and+disease.">Biochemistry of articular cartilage in health and disease.</a> Clinical Biochemistry. 25, 155-163 (1992).</li><li>Neu, C. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+interface+of+functional+biotribology+and+regenerative+medicine+in+synovial+joints.">The interface of functional biotribology and regenerative medicine in synovial joints.</a> Tissue Engineering Part B: Reviews. 14, 235-247 (2008).</li><li>Demarteau, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+compression+of+cartilage+constructs+engineered+from+expanded+human+articular+chondrocytes.">Dynamic compression of cartilage constructs engineered from expanded human articular chondrocytes.</a> Biochemical and Biophysical Research Communications. 310, 580-588 (2003).</li><li>Waldman, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+intermittent+compressive+stimulation+improves+the+composition+and+mechanical+properties+of+tissue-engineered+cartilage.">Long-term intermittent compressive stimulation improves the composition and mechanical properties of tissue-engineered cartilage.</a> Tissue Engineering. 10, 1323-1331 (2004).</li><li>Hunter, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+compression+of+chondrocyte-seeded+fibrin+gels:+effects+on+matrix+accumulation+and+mechanical+stiffness.">Dynamic compression of chondrocyte-seeded fibrin gels: effects on matrix accumulation and mechanical stiffness.</a> Osteoarthritis and Cartilage. 12, 117-130 (2004).</li><li>Buschmann, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+compression+modulates+matrix+biosynthesis+in+chondrocyte/agarose+culture.">Mechanical compression modulates matrix biosynthesis in chondrocyte/agarose culture.</a> Journal of Cell Science. 108 (Pt 4), 1497-1508 (1995).</li><li>Quinn, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+compression+alters+proteoglycan+deposition+and+matrix+deformation+around+individual+cells+in+cartilage+explants.">Mechanical compression alters proteoglycan deposition and matrix deformation around individual cells in cartilage explants.</a> Journal of Cell Science. 111 (Pt 5), 573-583 (1998).</li><li>Kuettner, K. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+cartilage+matrix+by+mammalian+chondrocytes+in+vitro.+I.+Isolation,+culture+characteristics,+and+morphology.">Synthesis of cartilage matrix by mammalian chondrocytes in vitro. I. Isolation, culture characteristics, and morphology.</a> The Journal of Cell Biology. 93, 743-750 (1982).</li><li>Lee, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+loading+of+chondrocytes+embedded+in+3D+constructs:+in+vitro+methods+for+assessment+of+morphological+and+metabolic+response+to+compressive+strain.">Mechanical loading of chondrocytes embedded in 3D constructs: in vitro methods for assessment of morphological and metabolic response to compressive strain.</a> Methods in Molecular Medicine. 100, 307-324 (2004).</li><li>McGowan, K. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemical+quantification+of+DNA+in+human+articular+and+septal+cartilage+using+PicoGreen+and+Hoechst+33258.">Biochemical quantification of DNA in human articular and septal cartilage using PicoGreen and Hoechst 33258.</a> Osteoarthritis and Cartilage. 10, 580-587 (2002).</li><li>Fan, J. C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+intermittent+static+biaxial+tensile+strains+on+tissue+engineered+cartilage.">The effect of intermittent static biaxial tensile strains on tissue engineered cartilage.</a> Annals of Biomedical Engineering. 38, 1672-1682 (2010).</li><li>Kaupp, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+vibrations+increase+the+proliferation+of+articular+chondrocytes+in+high-density+culture.">Mechanical vibrations increase the proliferation of articular chondrocytes in high-density culture.</a> Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. 222, 695-703 (2008).</li><li>Waldman, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+intermittent+shear+deformation+improves+the+quality+of+cartilaginous+tissue+formed+in+vitro.">Long-term intermittent shear deformation improves the quality of cartilaginous tissue formed in vitro.</a> Journal of Orthopaedic Research. 21, 590-596 (2003).</li><li>Waldman, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+single+application+of+cyclic+loading+can+accelerate+matrix+deposition+and+enhance+the+properties+of+tissue-engineered+cartilage.">A single application of cyclic loading can accelerate matrix deposition and enhance the properties of tissue-engineered cartilage.</a> Osteoarthritis and Cartilage. 14, 323-330 (2006).</li><li>Kisiday, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+dynamic+compressive+loading+on+chondrocyte+biosynthesis+in+self-assembling+peptide+scaffolds.">Effects of dynamic compressive loading on chondrocyte biosynthesis in self-assembling peptide scaffolds.</a> Journal of Biomechanics. 37, 595-604 (2004).</li><li>Chowdhury, T. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+regulation+of+chondrocyte+metabolism+in+agarose+constructs+subjected+to+dynamic+compression.">Temporal regulation of chondrocyte metabolism in agarose constructs subjected to dynamic compression.</a> Archives of Biochemistry and Biophysics. 417, 105-111 (2003).</li></ol>

Keine Interessenskonflikte erklärt.

<html> Das beschriebene Verfahren für das Auftragen kontrollierter mechanische Reize auf Zellen seeded Agarose Hydrogele ermöglicht die direkte Untersuchung der Auswirkungen von dynamischen Druckkräfte auf Chondrozytenmetabolismus. Die Verwendung des kundenspezifischen Prüfstand in Verbindung mit den Halteringen versehen seitliche Beschränkung für die Konstrukte, um mögliche Probleme der Probe Kippen zu vermeiden. Die Verwendung von dead-gewichtete Belastung Platten durch Mengen Crews gesichert gewährleistet den ...

<table border="1"><tbody><tr><td> Name des Reagens oder Ausrüstung </td><td> Firma </td><td> Katalog-Nummer </td><td> Kommentare (optional) </td></tr><tr><td> Ham-F-12 </td><td> Thermo Fisher Scientific </td><td> SH3001002 </td><td></td></tr><tr><td> Collagenase A </td><td> Sigma Aldrich Ltd </td><td> C0130 </td><td></td></tr><tr><td> Protease </td><td> Sigma Aldrich Ltd </td><td> P5147 </td><td></td></tr><tr><td> Fötales Rinderserum </td><td> Sigma Aldrich Ltd </td><td> F1051 </td><td></td></tr><tr><td> Ascorbat </td><td> Sigma Aldrich Ltd </td><td> A4034 </td><td></td></tr><tr><td> Antibiotika / Antimykotika </td><td> Sigma Aldrich Ltd </td><td> A5955 </td><td></td></tr><tr><td> HEPES </td><td> Bioshop Canada Ltd </td><td> HEP001 </td><td></td></tr><tr><td> Trypanblau </td><td> Sigma Aldrich Ltd </td><td> 93595 </td><td></td></tr><tr><td> Reichert Hell-Line Hämazytometer </td><td> Hausser Scientific </td><td> 1490 </td><td></td></tr><tr><td> Quant-iT PicoGreen </td><td> Invitrogen </td><td> P7589 </td><td></td></tr><tr><td> Papain aus Papaya Latex </td><td> Sigma Aldrich Ltd </td><td> P3125 </td><td></td></tr><tr><td> Ammoniumacetat </td><td> Sigma Aldrich Ltd </td><td> A1542 </td><td></td></tr><tr><td> Ethyldiaminetetraacetic Säure </td><td> Sigma Aldrich Ltd </td><td> E9884 </td><td></td></tr><tr><td> DL-Dithiothreitol </td><td> Sigma Aldrich Ltd </td><td> 43819 </td><td></td></tr><tr><td> Agarose mit niedrigem Schmelzpunkt, Typ VII </td><td> Sigma Aldrich Ltd </td><td> A9045 </td><td></td></tr> &lt;tr&gt; <td> Mesh-Screen (200) Filter </td><td> Sigma Aldrich Ltd </td><td> S4145 </td><td></td></tr><tr><td> Mach-1 Mikromechanische Tester </td><td> Biomomentum Inc. </td><td> V500cs </td><td></td></tr><tr><td> Compression Loading Jig </td><td> Custom-built </td><td></td><td> Ein Produkt ähnlich könnte Biomomentum Inc. geliefert werden </td></tr><tr><td> Falcon 24 Well Zellkulturplatten </td><td> Thermo Fisher Scientific </td><td> B353047 </td><td></td></tr><tr><td> β-Flüssigkeits-Szintillationszähler </td><td> Beckman Coulter </td><td> LS6500 </td><td></td></tr><tr><td> [3H] Proline </td><td> Perkin-Elmer </td><td> NET323005MC </td><td></td></tr><tr><td> [35S] Sulfur </td><td> Perkin-Elmer </td><td> NEX041005MC </td><td></td></tr></tbody></table>

mechanical stimulation of chondrocyte-agarose hydrogels

Gelenkknorpel leidet unter einer begrenzten Kapazität, wenn Reparatur durch mechanische Insult oder abgebaute durch Krankheiten, wie Osteoarthritis beschädigt. Um diesem Mangel abzuhelfen, haben mehrere medizinische Eingriffe entwickelt. Eine solche Methode ist, um den beschädigten Bereich mit Tissue-Engineering Knorpel wieder auftauchen, aber die gezüchteten Gewebe in der Regel fehlen die biochemischen Eigenschaften und Haltbarkeit von nativen Knorpel Frage der langfristigen Überlebensfähigkeit. Dies beschränkt die Anwendung von Knorpelgewebe Engineering zur Reparatur von kleinen fokalen Fehlern, die sich auf das umgebende Gewebe, um die implantierte Material zu schützen. Um die Eigenschaften des entwickelten Gewebe zu verbessern, ist eine mechanische Stimulation eine beliebte Methode verwendet, um die Synthese von Knorpel extrazellulären Matrix sowie die resultierenden mechanischen Eigenschaften des gezüchteten Gewebe zu verbessern. Mechanische Stimulation gilt Kräfte auf das Gewebe konstruiert analog zu den erfahrensten in vivo. Diesbasiert auf der Prämisse, dass die mechanischen Umgebung, teilweise, reguliert die Entwicklung und Wartung von nativem Gewebe 1,2 basiert. Die am häufigsten angewandte Form der mechanischen Stimulation im Knorpel Tissue engineering ist Dynamikkompression bei physiologischem Stämme von etwa 5-20% bei einer Frequenz von 1 Hz 1,3. Mehrere Studien haben die Auswirkungen der dynamischen Kompression untersucht und haben gezeigt, dass es einen positiven Effekt auf Chondrozytenmetabolismus und Biosynthese haben, letztendlich auch die funktionellen Eigenschaften des entwickelten Gewebe 4-8. In diesem Papier zeigen wir die Methode zur mechanischen Stimulierung Chondrozyten-Agarose Hydrogel Konstrukten unter dynamischer Kompression und Analyse der Veränderungen in der Biosynthese durch biochemische und radioaktiven Assays. Dieses Verfahren kann auch ohne weiteres modifiziert werden, um alle möglicherweise induzierte Veränderungen in zelluläre Reaktion als Folge der mechanischen Reizen zu beurteilen.

Watch this Scientific Journal Video about Mechanical Stimulation of Chondrocyte-agarose Hydrogels at JoVE.com

Mechanical Stimulation of Chondrocyte-agarose Hydrogels

Die Biosynthese von knorpeligen extrazellulären Matrix durch Chondrocyten können durch Einwirkung mechanischer Reize beeinflußt werden. Diese Methode beschreibt die Technik der Anwendung dynamisch Druckspannungen zu Chondrozyten in 3D-Konstrukte und die Auswertung der induzierten Veränderungen in Chondrozytenmetabolismus verkapselt.

Mechanische Stimulation der Chondrozyten-Agarose Hydrogele

Articular cartilage suffers from a limited repair capacity when damaged by mechanical insult or degraded by disease, such as osteoarthritis. To remedy ...

mechanical-stimulation-of-chondrocyte-agarose-hydrogels

Research

JoVE Journal

Biology

11.6K Aufrufe.  Queen's University. Die Biosynthese von knorpeligen extrazellulären Matrix durch Chondrocyten können durch Einwirkung mechanischer Reize beeinflußt werden. Diese Methode beschreibt die Technik der Anwendung dynamisch Druckspannungen zu Chondrozyten in 3D-Konstrukte und die Auswertung der induzierten Veränderungen in Chondrozytenmetabolismus verkapselt.

Serie: Mechanical Stimulation of Chondrocyte-agarose Hydrogels

Ex vivo Mechanical Loading of Tendon

Injuries to the tendon (e.g., wrist tendonitis, epicondyltis) due to overuse are common in sports activities and the workplace. Most are associated with repetitive, high force hand activities. The mechanisms of cellular and structural damage due to cyclical loading are not well known. The purpose of this video is to present a new system that can simultaneously load four tendons in tissue culture. The video describes the methods of sterile tissue harvest and how the tendons are loaded onto a clamping system that is subsequently immersed into media and maintained at 37&deg;C. One clamp is fixed while the other one is moved with a linear actuator. Tendon tensile force is monitored with a load cell in series with the mobile clamp. The actuators are controlled with a LabView program. The four tendons can be repetitively loaded with different patterns of loading, repetition rate, rate of loading, and duration. Loading can continue for a few minutes to 48 hours. At the end of loading, the tendons are removed and the mid-substance extracted for biochemical analyses. This system allows for the investigation of the effects of loading patterns on gene expression and structural changes in tendon. Ultimately, mechanisms of injury due to overuse can be studies with the findings applied to treatment and prevention.

A new in vitro system for simultaneously loading four tendons in culture is described.

Ex vivo mechanische Belastung der Sehnen

Injuries to the tendon (e.g., wrist tendonitis, epicondyltis) due to overuse are common in sports activities and the workplace.  Most are associated with ...

Forschung

Biologie

Mechanical Stimulation of Stem Cells Using Cyclic Uniaxial Strain

The role of mechanical forces in the development and maintenance of biological tissues is well documented, including several mechanically regulated phenomena such as bone remodeling, muscular hypertrophy, and smooth muscle cell plasticity. However, the forces involved are often extremely complex and difficult to monitor and control in vivo. To better investigate the effects of mechanical forces on cells, we have developed an in vitro method for applying uniaxial cyclic tensile strain to adherent cells cultured on elastic membranes. This method utilizes a custom-designed bioreactor with a motorized cam-rotor system to apply the desired force. Here we present a step-by-step video protocol demonstrating how to assemble the various components of each "stretch chamber", including, in this case, a silicone membrane with micropatterned topography to orient the cells with the direction of the strain. We also describe procedures for sterilizing the chambers, seeding cells onto the membrane, latching the chamber into the bioreactor, and adjusting the mechanical parameters (i.e. magnitude and rate of strain). The procedures outlined in this particular protocol are specific for seeding human mesenchymal stem cells onto silicone membranes with 10 &micro;m wide channels oriented parallel to the direction of strain. However, the methods and materials presented in this system are flexible enough to accommodate a number of variations on this theme: strain rate, magnitude, duration, cell type, membrane topography, membrane coating, etc. can all be tailored to the desired application or outcome. This is a robust method for investigating the effects of uniaxial tensile strain applied to cells in vitro.

It is widely understood that mechanical forces in the body can influence cell differentiation and proliferation. Here we present a video protocol demonstrating the use of a custom-built bioreactor for delivering uniaxial cyclic tensile strain to stem cells cultured on flexible micropatterned substrates.

Mechanische Stimulation von Stammzellen unter Verwendung cyclischer uniaxiale Dehnung

The role of mechanical forces in the development and maintenance of biological tissues is well documented, including several mechanically regulated ...

Cellular Encapsulation in 3D Hydrogels for Tissue Engineering 

The 3D encapsulation of cells within hydrogels represents an increasingly important and popular technique for culturing cells and towards the development of constructs for tissue engineering. This environment better mimics what cells observe in vivo, compared to standard tissue culture, due to the tissue-like properties and 3D environment. Synthetic polymeric hydrogels are water-swollen networks that can be designed to be stable or to degrade through hydrolysis or proteolysis as new tissue is deposited by encapsulated cells. A wide variety of polymers have been explored for these applications, such as poly(ethylene glycol) and hyaluronic acid. Most commonly, the polymer is functionalized with reactive groups such as methacrylates or acrylates capable of undergoing crosslinking through various mechanisms. In the past decade, much progress has been made in engineering these microenvironments - e.g., via the physical or pendant covalent incorporation of biochemical cues - to improve viability and direct cellular phenotype, including the differentiation of encapsulated stem cells (Burdick et al.).
The following methods for the 3D encapsulation of cells have been optimized in our and other laboratories to maximize cytocompatibility and minimize the number of hydrogel processing steps. In the following protocols (see Figure 1 for an illustration of the procedure), it is assumed that functionalized polymers capable of undergoing crosslinking are already in hand; excellent reviews of polymer chemistry as applied to the field of tissue engineering may be found elsewhere (Burdick et al.) and these methods are compatible with a range of polymer types. Further, the Michael-type addition (see Lutolf et al.) and light-initiated free radical (see Elisseeff et al.) mechanisms focused on here constitute only a small portion of the reported crosslinking techniques. Mixed mode crosslinking, in which a portion of reactive groups is first consumed by addition crosslinking and followed by a radical mechanism, is another commonly used and powerful paradigm for directing the phenotype of encapsulated cells (Khetan et al., Salinas et al.).

Cellular Encapsulation in 3D Hydrogels for Tissue Engineering

We present protocols for the 3-dimensional (3D) encapsulation of cells within synthetic hydrogels. The encapsulation procedure is outlined for two commonly used methods of crosslinking (michael-type addition and light-initiated free radical mechanisms), as well as a number of techniques for assessing encapsulated cell behavior.

Cellular Encapsulation in 3D Hydrogele für Tissue Engineering

The 3D encapsulation of cells within hydrogels represents an increasingly important and popular technique for culturing cells and towards the development ...

Live Cell Response to Mechanical Stimulation Studied by Integrated Optical and Atomic Force Microscopy

To understand the mechanism by which living cells sense mechanical forces, and how they respond and adapt to their environment, a new technology able to investigate cells behavior at sub-cellular level with high spatial and temporal resolution was developed. Thus, an atomic force microscope (AFM) was integrated with total internal reflection fluorescence (TIRF) microscopy and fast-spinning disk (FSD) confocal microscopy. The integrated system is broadly applicable across a wide range of molecular dynamic studies in any adherent live cells, allowing direct optical imaging of cell responses to mechanical stimulation in real-time. Significant rearrangement of the actin filaments and focal adhesions was shown due to local mechanical stimulation at the apical cell surface that induced changes into the cellular structure throughout the cell body. These innovative techniques will provide new information for understanding live cell restructuring and dynamics in response to mechanical force. A detailed protocol and a representative data set that show live cell response to mechanical stimulation are presented.

This paper aims to instruct the reader in the operation of an integrated atomic force-optical imaging microscope for mechanical stimulation of live cells in culture. A step-by-step protocol is presented. A representative data set that shows live cell response to mechanical stimulation is presented.

Live Cell Reaktion auf mechanische Stimulation von Integrated Optical und Atomic Force Microscopy Studium

To understand the mechanism by which living cells sense mechanical forces, and how they respond and adapt to their environment, a new technology able to ...

Mechanical Stimulation-induced Calcium Wave Propagation in Cell Monolayers: The Example of Bovine Corneal Endothelial Cells

Intercellular communication is essential for the coordination of physiological processes between cells in a variety of organs and tissues, including the brain, liver, retina, cochlea and vasculature. In experimental settings, intercellular Ca2+-waves can be elicited by applying a mechanical stimulus to a single cell. This leads to the release of the intracellular signaling molecules IP3 and Ca2+ that initiate the propagation of the Ca2+-wave concentrically from the mechanically stimulated cell to the neighboring cells. The main molecular pathways that control intercellular Ca2+-wave propagation are provided by gap junction channels through the direct transfer of IP3 and by hemichannels through the release of ATP. Identification and characterization of the properties and regulation of different connexin and pannexin isoforms as gap junction channels and hemichannels are allowed by the quantification of the spread of the intercellular Ca2+-wave, siRNA, and the use of inhibitors of gap junction channels and hemichannels. Here, we describe a method to measure intercellular Ca2+-wave in monolayers of primary corneal endothelial cells loaded with Fluo4-AM in response to a controlled and localized mechanical stimulus provoked by an acute, short-lasting deformation of the cell as a result of touching the cell membrane with a micromanipulator-controlled glass micropipette with a tip diameter of less than 1 &mu;m. We also describe the isolation of primary bovine corneal endothelial cells and its use as model system to assess Cx43-hemichannel activity as the driven force for intercellular Ca2+-waves through the release of ATP. Finally, we discuss the use, advantages, limitations and alternatives of this method in the context of gap junction channel and hemichannel research.

Intercellular Ca2+-waves are driven by gap junction channels and hemichannels. Here, we describe a method to measure intercellular Ca2+-waves in cell monolayers in response to a local single-cell mechanical stimulus and its application to investigate the properties and regulation of gap junction channels and hemichannels.

Mechanische Stimulation induzierte Calcium Wellenausbreitung in Zellmonoschichten: Das Beispiel Bovine Endothelzellen

Intercellular communication is essential for the coordination of physiological processes between cells in a variety of organs and tissues, including the ...

Preparation of DNA-crosslinked Polyacrylamide Hydrogels

Mechanobiology is an emerging scientific area that addresses the critical role of physical cues in directing cell morphology and function. For example, the effect of tissue elasticity on cell function is a major area of mechanobiology research because tissue stiffness modulates with disease, development, and injury. Static tissue-mimicking materials, or materials that cannot alter stiffness once cells are plated, are predominately used to investigate the effects of tissue stiffness on cell functions. While information gathered from static studies is valuable, these studies are not indicative of the dynamic nature of the cellular microenvironment in vivo. To better address the effects of dynamic stiffness on cell function, we developed a DNA-crosslinked polyacrylamide hydrogel system (DNA gels). Unlike other dynamic substrates, DNA gels have the ability to decrease or increase in stiffness after fabrication without stimuli. DNA gels consist of DNA crosslinks that are polymerized into a polyacrylamide backbone. Adding and removing crosslinks via delivery of single-stranded DNA allows temporal, spatial, and reversible control of gel elasticity. We have shown in previous reports that dynamic modulation of DNA gel elasticity influences fibroblast and neuron behavior. In this report and video, we provide a schematic that describes the DNA gel crosslinking mechanisms and step-by-step instructions on the preparation DNA gels.

Our laboratory has developed DNA-crosslinked polyacrylamide hydrogels, a dynamic hydrogel system, to better understand the effects of modulating tissue stiffness on cell function. Here, we provide schematics, descriptions, and protocols to prepare these hydrogels.

Herstellung von DNA-vernetztem Polyacrylamid, Hydrogele

Mechanobiology is an emerging scientific area that addresses the critical role of physical cues in directing cell morphology and function. For example, ...

Multifunctional, Micropipette-based Method for Incorporation And Stimulation of Bacterial Mechanosensitive Ion Channels in Droplet Interface Bilayers

MscL, a large conductance mechanosensitive channel (MSC), is a ubiquitous osmolyte release valve that helps bacteria survive abrupt hypo-osmotic shocks. It has been discovered and rigorously studied using the patch-clamp technique for almost three decades. Its basic role of translating tension applied to the cell membrane into permeability response makes it a strong candidate to function as a mechanoelectrical transducer in artificial membrane-based biomolecular devices. Serving as building blocks to such devices, droplet interface bilayers (DIBs) can be used as a new platform for the incorporation and stimulation of MscL channels. Here, we describe a micropipette-based method to form DIBs and measure the activity of the incorporated MscL channels. This method consists of lipid-encased aqueous droplets anchored to the tips of two opposing (coaxially positioned) borosilicate glass micropipettes. When droplets are brought into contact, a lipid bilayer interface is formed. This technique offers control over the chemical composition and the size of each droplet, as well as the dimensions of the bilayer interface. Having one of the micropipettes attached to a harmonic piezoelectric actuator provides the ability to deliver a desired oscillatory stimulus. Through analysis of the shapes of the droplets during deformation, the tension created at the interface can be estimated. Using this technique, the first activity of MscL channels in a DIB system is reported. Besides MS channels, activities of other types of channels can be studied using this method, proving the multi-functionality of this platform. The method presented here enables the measurement of fundamental membrane properties, provides a greater control over the formation of symmetric and asymmetric membranes, and is an alternative way to stimulate and study mechanosensitive channels.

Bacterial mechanosensitive channels can be used as mechanoelectrical transducers in biomolecular devices. Droplet interface bilayers (DIBs), cell-inspired building blocks to such devices, represent new platforms to incorporate and stimulate mechanosensitive channels. Here, we demonstrate a new micropipette-based method of forming DIBs, allowing the study of mechanosensitive channels under mechanical stimulation.

Multifunktionale, Mikropipette-basierte Methode für den Einbau und Stimulation der bakteriellen mechanosensitiven Ionenkanäle in Droplet Schnittstelle Bilayers

MscL, a large conductance mechanosensitive channel (MSC), is a ubiquitous osmolyte release valve that helps bacteria survive abrupt hypo-osmotic shocks. ...

FRET Imaging in Three-dimensional Hydrogels

Imaging of F&#246;rster resonance energy transfer (FRET)&#160;is a powerful tool for examining cell biology in real-time. Studies utilizing FRET commonly employ two-dimensional (2D) culture, which does not mimic the three-dimensional (3D) cellular microenvironment. A method to perform quenched emission FRET imaging using conventional widefield epifluorescence microscopy of cells within a 3D hydrogel environment is presented. Here an analysis method for ratiometric FRET probes that yields linear ratios over the probe activation range is described. Measurement of intracellular cyclic adenosine monophosphate (cAMP) levels is demonstrated in chondrocytes under forskolin stimulation using a probe for EPAC1 activation (ICUE1) and the ability to detect differences in cAMP signaling dependent on hydrogel material type, herein a photocrosslinking hydrogel (PC-gel, polyethylene glycol dimethacrylate) and a thermoresponsive hydrogel (TR-gel). Compared with 2D FRET methods, this method requires little additional work. Laboratories already utilizing FRET imaging in 2D can easily adopt this method to perform cellular studies in a 3D microenvironment. It can further be applied to high throughput drug screening in engineered 3D microtissues. Additionally, it is compatible with other forms of FRET imaging, such as anisotropy measurement and fluorescence lifetime imaging (FLIM), and with advanced microscopy platforms using confocal, pulsed, or modulated illumination.

F&#246;rster resonance energy transfer (FRET) imaging is a powerful tool for real-time cell biology studies. Here a method for FRET imaging cells in physiologic three-dimensional (3D) hydrogel microenvironments using conventional epifluorescence microscopy is presented. An analysis for ratiometric FRET probes that yields linear ratios over the activation range is described.

FRET-Imaging im dreidimensionalen Hydrogelen

Imaging of F&#246;rster resonance energy transfer (FRET)&#160;is a powerful tool for examining cell biology in real-time. Studies utilizing FRET commonly ...

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium discoideum revealed that a complex signal transduction network of parallel pathways amplifies the response to chemoattractants, and leads to biased actin polymerization and protrusion of a pseudopod in the direction of a gradient. In contrast, molecular mechanisms driving other types of directed migration, for example, due to exposure to shear flow or electric fields, are not known. Many regulators of chemotaxis exhibit localization at the leading or lagging edge of a migrating cell, as well as show transient changes in localization or activation following global stimulation with a chemoattractant. To understand the molecular mechanisms of other types of directed migration we developed a method that allows examination of cellular response to acute mechanical stimulation based on brief (2 - 5 s) exposure to shear flow. This stimulation can be delivered in a channel while imaging cells expressing fluorescently-labeled biosensors to examine individual cell behavior. Additionally, cell population can be stimulated in a plate, lysed, and immunoblotted using antibodies that recognize active versions of proteins of interest. By combining both assays, one can examine a wide array of molecules activated by changes in subcellular localization and/or phosphorylation. Using this method we determined that acute mechanical stimulation triggers activation of the chemotactic signal transduction and actin cytoskeleton networks. The ability to examine cellular responses to acute mechanical stimulation is important for understanding the initiating events necessary for shear flow-induced motility. This approach also provides a tool for studying the chemotactic signal transduction network without the confounding influence of the chemoattractant receptor.

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Here we describe methods for assessing cellular response to acute mechanical stimulation. In the microscopy-based assay, we examine localization of fluorescently-labeled biosensors following brief stimulation with shear flow. We also test activation of various proteins of interest in response to acute mechanical stimulation biochemically.

Bewertung von Dictyostelium Discoideum Reaktion auf akute mechanische Stimulation

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium ...

Proteolytically Degraded Alginate Hydrogels and Hydrophobic Microbioreactors for Porcine Oocyte Encapsulation

In reproductive biology, the biotechnology revolution that began with artificial insemination and embryo transfer technology led to the development of assisted reproduction techniques such as oocyte in vitro maturation (IVM), in vitro fertilization (IVF) and cloning of domestic animals by nuclear transfer from somatic cell. IVM is the method particularly of significance. It is the platform technology for the supply of mature, good quality oocytes for applications such as reduction of the generation interval in commercially important or endangered species, research concerning in vitro human reproduction, and production of transgenic animals for cell therapies. The term oocyte quality includes its competence to complete maturation, be fertilized, thereby resulting in healthy offspring. This means that oocytes of good quality are paramount for successful fertilization including IVF procedures. This poses many difficulties to develop a reliable culture method that would support growth not only of human oocytes but also of other large mammalian species. The first step in IVM is the in vitro culture of oocytes. This work describes two protocols for the 3D culture of porcine oocytes. In the first, 3D model cumulus-oocyte complexes (COCs) are encapsulated in a fibrin-alginate bead interpenetrating network, in which a mixture of fibrin and alginate are gelled simultaneously. In the second one, COCs are suspended in a drop of medium and encapsulated with fluorinated ethylene propylene (FEP; a copolymer of hexafluoropropylene and tetrafluoroethylene) powder particles to form microbioreactors defined as Liquid Marbles (LM). Both 3D systems maintain the gaseous in vitro culture environment. They also maintain COCs 3D organization by preventing their flattening and consequent disruption of gap junctions, thereby preserving the functional relationship between the oocyte, and surrounding follicular cells.

Presented here are two protocols for the encapsulation of porcine oocytes in 3D culture conditions. In the first, cumulus-oocyte complexes (COCs) are encapsulated in fibrin-alginate beads. In the second, they are enclosed with fluorinated ethylene propylene powder particles (microbioreactors). Both systems ensure optimal conditions to maintain their 3D organization.

Proteolytisch abgebaute Alginat-Hydrogele und hydrophobe Mikrobioreaktoren zur Poren-Oozyten-Verkapselung

In reproductive biology, the biotechnology revolution that began with artificial insemination and embryo transfer technology led to the development of ...